The introduction and spread of non-indigenous species (NIS) in marine ecosystems accelerated during the twentieth century owing to human activities, notably international shipping. Genetic analysis has proven useful in understanding the invasion history and dynamics of colonizing NIS and identifying their source population(s). Here we investigated sequence variation in the nuclear ribosomal Internal Transcribed Spacer region of the ctenophore Mnemiopsis leidyi, a species considered one of the most invasive globally. We surveyed four populations from the native distribution range along the Atlantic coasts of the United States and South America, as well as six populations in the introduced range from the Black, Azov, Caspian and Baltic seas. Allelic and nucleotide diversity of introduced populations were comparable to those of native populations from which they were likely drawn. Introduced populations typically exhibited lower genetic differentiation (F ST = -0.014-0.421) than native populations (F ST = 0.324-0.688). Population genetic analyses supported the invasion of Eurasia from at least two different pathways, the first from the Gulf of Mexico (e.g., Tampa Bay) to the Black Sea and thence to the Caspian Sea, the second from the northern part of the native distribution range (e.g., Narragansett Bay) to the Baltic Sea. The relatively high genetic diversity observed in introduced populations is consistent with large inocula and/or multiple invasions, both of which are possible given ballast water transport and the extensive native distribution of the ctenophore in the Atlantic Ocean.

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Different types of cardiotoxin (I-V and n) were isolated and purified from the venom of the Taiwan cobra (Naja naja atra). The effects of these cardiotoxins were studied on membrane-bound acetylcholinesterase, which was isolated from a sheep's brain cortex. The results showed that cardiotoxins I-III, V, and n activated the enzyme by modification of substrate inhibition, but cardiotoxin IV's reaction was different. The inhibition and activation of acetylcholinesterase were linked to the functions of the hydrophobicity index, presence of a cationic cluster, and the accessible arginine residue. Our results indicate that Cardiotoxins have neither a cationic cluster nor an arginine residue in their surface area of loop I; therefore, in contrast to fasciculin, cardiotoxins are attached by loop II to the peripheral site of the enzyme. As a result, fasciculin seems to stabilize nonfunctional conformation, but cardiotoxins seem to stabilize the functional conformation of the enzyme. Based on our experimental and theoretical findings, similar secondary and tertiary structures of cardiotoxins and fasciculin seem to have an opposite function once they interact with acetylcholinesterase.

Problem statement: Fatty acid content and composition in mollusks is a function of their feeding diversity. Chabahar bay located in the northern part of Oman sea in Indian ocean provides high rates of primary productivity and a diverse food source for mollusks in this area. Identification of fatty acid compositions of Chiton lamyi and study their seasonal changes in the intertidal zone of Chabahar bay. Study the meat quality by n-6: n-3 ratios calculation throughout the year. Approach: Chiton lamyi species analyzed seasonally for its fatty acid compositions in foot and internal tissue separately by GC/MS chromatography. Temperature and nutrients measured monthly for evaluating their effects on investigated seasonal variations of fatty acids. Pearson analysis showed effects of measured environmental factors on studied fatty acids composition. n-6: n-3 ratio calculated seasonally in order to study meat quality. Results: Thirteen fatty acids identified in foot and internal tissue of Chiton lamyi. The major Saturated Fatty Acids (SFAs) were myristic, palmitic and stearic acids. The major MonoUnsaturated Fatty Acids (MUFAs) were palmitoleic, oleic and 11-eicosenoic acids and PolyUnsaturated Fatty Acids (PUFAs) were linoleic, eicosapentaenoic and arachidonic acids. Palmitic acid was the most abundant in this species. Fatty acid contents of foot and internal tissue of Chiton lamyi were similar but their seasonal variations were different. Pearson analysis showed correlation among palmitic and oleic acids with silicate; oleic acid with phosphate; Linoleic and arachidonic acids with nitrate in Chiton lamyi internal tissues, but no correlation observed in foot. Although temperature showed correlation with heptadecanoic and methyl-heptadecanoic acids in Chiton lamyi foot, no correlation found in internal tissues. Also, n-6: n-3 ratio calculations showed domination of n-3 fatty acid over n-6 only in spring. Conclusion: Fatty acid variations were not same at different organs and environmental factors could have opposite effects on them in this species. Also, n-6: n-3 ratio showed the lack of food loads throughout the year except in spring for this species. These findings can lead the best exploitation periods for such marine mollusks.

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